This invention relates to a surgical instrument for the subcutaneous insertion and removal of an injection reservoir used for the inflation of an implantable prosthesis such as a tissue expander.
Inflatable prostheses such as mammary prostheses and tissue expanders can be inflated subcutaneously by two commonly available means. The first means is via a resealable valve mounted directly on the surface of the prosthesis itself to permit introduction of a fluid into the prosthesis via a hypodermic syringe. The second means for inflating such a prosthesis is via an injection reservoir which is not itself expandable and has a self-sealing area designed to be punctured by a hypodermic needle to permit introduction of a fluid into the hollow center of the injection reservoir which then travels through an elongated fluid conduit such as a piece of tubing over to the inflatable prosthesis itself. Remotely placed injection reservoirs of the second type have also been referred to as "remote valves", "subcutaneous injection sites", "valve domes" and "puncture housings"; the term "injection reservoir" shall be used herein to designate such inflation means. Each type of inflation means has its own advantages and disadvantages.
An implant such as a tissue expander with a remote injection reservoir may be selected because, for example, of the ease with which the injection reservoir can be found by palpation or to reduce the possibility that the prosthesis envelope itself may be accidentally damaged during inflation by a needle puncture. To implant such a prosthesis, the surgeon must not only create a subcutaneous pocket for the prosthesis itself, but must also create a pocket for the injection reservoir and the tubing connecting it to the tissue expander.
It is preferable to minimize the number of incisions made through the skin during a surgical procedure for obvious reasons; therefore a single incision is normally desirable and is used to create a subcutaneous pocket for the inflatable envelope of the tissue expander as well as the injection reservoir. This can create some difficulty for the surgeon since the injection reservoir must generally be passed along a narrow subcutaneous tunnel not much larger than the injection reservoir itself to avoid disturbing any more tissue than is necessary. The injection reservoir may tip to one side or the other as it is pushed into place or may even flip over during the insertion procedure.
Once in place, the injection reservoir generally remains in place for a period of time numbering days to weeks and during that time a capsule is observed to form around the injection reservoir as well as the tubing and the inflatable portion of the tissue expander. The formation of this capsule is a natural response to the presence of the implanted prosthesis, but creates difficulties for the surgeon when the injection reservoir is to be removed if only one incision through the skin is to be used. People vary in the type of capsules produced and it is sometimes difficult to remove the injection reservoir without making a second incision near the injection reservoir if a thick or tight capsule has formed.